The present invention relates to a variable displacement swash plate type compressor adapted for use in an air conditioning system for a vehicle, and more particularly to a tapered swash plate which effectively causes constant bearing contact between the swash plate and the associated pistons during any changes in the inclination of the swash plate.
Variable displacement swash plate type compressors typically include a cylinder block provided with a number of cylinders, a piston disposed in each of the cylinders of the cylinder block, a crankcase sealingly disposed on one end of the cylinder block, a rotatably supported drive shaft, and a swash plate. The swash plate is adapted to be rotated by the drive shaft. The rotation of the swash plate is effective to reciprocatively drive the pistons. The length of the stroke of the pistons is varied by the inclination of the swash plate.
In the prior art, a variety of structures have been disclosed for operatively connecting the swash plate and the pistons. Typically, a pair of semi-spherical shoes is disposed in a bridge portion of the pistons and slidingly engages a swash plate of uniform thickness. Specifically, the flat bearing surface of a semi-spherical shoe slidably engages the swash plate, with the spherical surface typically disposed in a concave shoe pocket in the bridge portion of each piston. As the swash plate is caused to slide along the flat bearing surface of the semi-spherical shoes of the pistons, friction is created causing undesirable heat and wear.
Prior art structures typically include a swash plate having machined surfaces adapted to engage the entire flat bearing surfaces of the semi-spherical shoes. A disadvantage of the prior art is that the swash plate must be of a specified diameter and weight to support the surface area of the semi-spherical shoes of the pistons. The flat bearing surfaces of the shoes must be polished, adding expense. In addition, the polished surfaces may also require surface hardening adding even more expense.
An object of the present invention is to produce a swash plate type compressor wherein the contacting surface area between the swash plate and each shoe is minimized thereby minimizing friction, heat, and wear.
The above, as well as other objects of the present invention, may be readily achieved by a variable displacement swash plate type compressor comprising: a cylinder block having a plurality of cylinders arranged radially therein; a plurality of pistons, each of the pistons reciprocatively disposed in each of the cylinders of the cylinder block; a cylinder head attached to the cylinder block and cooperating with the cylinder block to define an airtight seal; a crankcase attached to the cylinder block and cooperating with the cylinder block to define an airtight sealed crank chamber; a drive shaft rotatably supported by the crankcase and the cylinder block in the crank chamber; bearing means disposed in a bridge portion of the pistons; and a swash plate adapted to be driven by the drive shaft, the swash plate having a central aperture, opposing sides, and a peripheral edge, the drive shaft extending through the aperture of the swash plate the opposing sides of the swash plate having tapered surfaces intermediate the central aperture and. the peripheral edge, the tapered surfaces causing the swash plate to remain in constant bearing contact with the bearing means as the inclination of the swash plate changes.